Most people think of search engine when they hear the word google. Although search engine is one of the biggest contribution from Google by becoming the yellow pages for the internet tubes. The impact of programs like AdSense is often misunderstood.
"Google AdSense is a free program that empowers online publishers to earn revenue by displaying relevant ads on a wide variety of online content".
AdSense has provided a great way for a large number of people to monetize their knowledge and as a result thousands of people have started sharing their knowledge on their websites or blogs. These AdSense powered websites have contributed in a big way to productivity of both the authors and immensely for the readers and therefore the economy.
You can read more about the impact of various products in this report published by Google. The impact of knowledge sharing is not documented in this report and that I believe would be biggest flaw of this report.